My UID is SugusX (South African) and I am new to Linux Mint but long ago worked on AIX V4 with Korn Shell.
Currrently using Linux Mint13 with Maya - very nice, except that sometimes running miultiple Firefox sessions the sytem freezescompletely. I am beginning to suspect my Huawei E1752 Dongle (3G Broadband). The only way out seems to be to hit reset button.

Question: Is there a key sequence (ie Shift-Ctrl-Backspace or something equally weird) which will break out of MAya or return a the system so sessions can be deleted
TIA

Ctrl+Alt-F1 to Ctrl-Alt-F6 should bring you to a tty session from where you can sort things out or at least do a clean reboot. Ctrl-Alt-F7 or Ctrl-Alt-F8 brings you back to the X session. Eventually hitting Alt-F2 and typing "r" + return may help also as it restarts your window manager.

The idea that Bill Gates has appeared like a knight in shining armour to lead all customers out of a mire of technological chaos neatly ignores the fact that it was he who, by peddling second-rate technology, led them into it in the first place.

Welcome to Linux Mint Indeed, Ctrl+Alt+F1 through F6 bring you to a virtual terminal from where you can kill any hanging processes if needed. If all else fails, you can press Ctrl+Alt+Backspace to kill your entire session and be taken back to the login screen. The kernel also has a, as it is known, "magic SysRQ key" from which you may shut down gracefully a non-responsive system. See https://en.wikipedia.org/wiki/Magic_SysRq_key for more about that. To kill just one program, you can also press Alt+F2 and run "xkill". That will turn your mouse cursor into a cross hairs. Left-clicking a window will kill the program that owns that window. Right-clicking will cancel the action. I usually bind the keyboard sequence Ctrl+Alt+Del to run xkill.